Another quake rattles North Korea nuclear testing grounds

A North Korea Scud-B missile is displayed at the Korea War Memorial Museum on August 26, 2017 in Seoul, South Korea.

A series of tremors and landslides near North Korea's nuclear test base likely mean the country's sixth and largest blast has destabilized the region, and the Punggye-ri nuclear site may not be used for much longer to test nuclear weapons, experts say.

A small quake was detected early on Friday near the North's nuclear test site, South Korea's weather agency said, but unlike quakes associated with nuclear tests, it did not appear to be manmade. The tremor was the latest in a string of at least three shocks to be observed since Pyongyang's Sept. 3 nuclear test, which caused a 6.3 magnitude earthquake.

Friday's quake was a magnitude 2.7 with a depth of 3 km in North Hamgyong Province in North Korea, the Korea Meteorological Administration said. The United States Geological Survey (USGS) measured the quake at 2.9 magnitude at a depth of 5 km.

The series of quakes has prompted experts and observers to suspect the last test - which the North claimed to be of a hydrogen bomb - may have damaged the mountainous location in the northwest tip of the country, where all of North Korea's six nuclear tests were conducted.

"The explosion from the Sept. 3 test had such power that the existing tunnels within the underground testing site might have caved in," said Kim So-gu, head researcher at the Korea Seismological Institute.

"I think the Punggye-ri region is now pretty saturated. If it goes ahead with another test in this area, it could risk radioactive pollution."

According to 38 North, a Washington-based project which monitors North Korea, numerous landslides throughout the nuclear test site have been detected via satellite images after the sixth test. These disturbances are more numerous and widespread than seen after any of the North's previous tests, 38 North said.